The present invention relates in general to route generation in vehicle navigation systems, and, more specifically, to route selection criteria including user selectable routing options such as a statistical risk index which allows the user to avoid or minimize the corresponding statistical risk along the generated route.
Vehicle navigation systems have become well known wherein a map database is used to provide navigational assistance to the driver of a vehicle. Based upon a current location and a desired destination, a navigation computer generates an optimum route between the two points. The route may then be displayed visually for the driver. Turn-by-turn instructions and/or a description of the route may be given visually and/or aurally.
Various techniques have been developed for constructing a route which is the most desirable according to predetermined optimization criteria. Typically, the map database is comprised of route segments, each segment connecting two endpoints or intersections. One widely used method for determining an optimal route is the Dijkstra method wherein each route segment in the map database has an associated cost or weight. The total weight of various potential routes between the current location and the destination are calculated and compared so that a route may be selected with the lowest overall weight.
In prior art systems, the optimization criteria is typically comprised of either the shortest route or the fastest route. In addition, selections have been provided for avoiding freeways, maximizing use of freeways, or avoiding tollways, for example. Thus, a route segment may have a plurality of weights and/or other attributes associated with it. For example, there may be a distance weight and a travel-time weight associated with a particular route segment. The generated route may be optimized using the various available weights according to the drivers preferred optimization. In addition, many prior art systems allow the driver to specify a specific route segment to be eliminated from consideration for use in a route, such as when a road is closed for construction or there is an error in the database. Nevertheless, drivers have had little control over route optimization criteria or how they are applied.
Navigation systems may be used to help a driver navigate through areas with which they are not familiar. Other than knowing that a route is optimized for distance, time or avoiding freeways or tollways, etc., the user of a prior art navigation system has not known the prevailing risk characteristics of the areas through which the route passes.